Despite the availability of technically advanced hearing aids, some of which are fully digital hearing aids, up to 80% of individuals who admittedly need hearing aids do not obtain them.
This has been true even though high-fidelity hearing aids are commercially available. One example of such a hearing aid is the K-AMP® hearing aid, elements of which are described, for example, in U.S. Pat. Nos. 4,170,720 and 5,131,046, and 5,144,675. Experimental testing has indicated that the K-AMP® hearing aid provides a fidelity that exceeds other digital or analog hearing aids. One measure of K-AMP® hearing aid's fidelity is that four members of the Chicago Symphony Orchestra—including a former concertmaster of the CSO and the principal of the 2nd violin section of the CSO—wore K-AMP® hearing aids on stage and off until they retired a few years ago. At one time, an estimated 18-20% of all hearing aids in the U.S. were K-AMP® hearing aids. As one internationally known professor stated: the K-AMP® “had an incredible and indelible worldwide influence on how hearing aids should be designed, selected and fitted” (Gus Mueller, Ph.D., quoted in Etymotic Research: 25 Years of Research & Product Development for the Ear, 2008). Unfortunately, K-AMP® hearing aids have required relatively expensive Class D amplifiers and receivers in order to provide their high-fidelity performance at high input levels. Examples of such Class D amplifiers and receivers are described, for example, in U.S. Pat. Nos. 4,592,087 and 4,689,819, issued to Killion.
Experimental testing has shown that the highest intelligibility in noise was obtained with hearing aids judged to have the highest sound quality, both by those with normal hearing and those with hearing loss (flat or sloping). In fact, the highest intelligibility was the natural sound of the open ear, which provided better fidelity and better intelligibility in noise than roughly half of the second-generation digital aids often described (inaccurately) as having “CD quality.” Experimental data supporting this finding is shown in FIG. 1A, which is a reproduction of FIGS. 7 and 8 from Killion M C, “Myths that Discourage Improvements in Hearing Aid Design,” The Hearing Review, 11, No. 1, 32-40, 70 (2004). The validity of these fidelity ratings is illustrated in FIG. 1B, where the fidelity rating listeners gave to the sound of some digital hearing aids is compared to the “25-Band Accuracy Score” calculated from the frequency response as described by Killion in 1979 (reference 8 in the “Myths” paper given above). Other experiments have attempted to rate the dollar value of the sound of some digital hearing aids. The sound quality of the majority of these aids was rated as being worth much less than their typical cost of $2,000-$3,000 each, as shown in FIG. 1C taken from the same paper. Dollar value for music reproduction is only one dimension in hearing aid value of course, but the relationship shown above between intelligibility in noise and fidelity suggests that part of the reason for hearing aids remaining in dresser drawers (i.e., going unused) may be unsatisfactory sound quality.
Nonetheless, the question of why 80% of those who need hearing aids go without them remains unanswered. There are many stated reasons for this phenomenon. Among them are: (1) a friend or relative purchased a hearing aid that ended up in a dresser drawer because it did not live up to the buyer's expectations; (2) the person needing a hearing aid didn't want to see a licensed professional (a licensed professional dispensing hearing aids is required by regulations in all but two states); and/or (3) a hearing aid was considered too expensive to afford, or simply too expensive. For example, one may hear comments such as “I can buy a top-of-the-line refrigerator for a few hundred dollars. Why should I have to pay more for a hearing aid?”
Whatever the reason, about 24 million people are going without hearing aids. Unfortunately, those persons and their friends and relatives suffer the consequences. As one author stated, “No one goes without hearing aids—they simply force their spouse to holler at them.” This makes for less than friendly and loving conversations: It is hard to feel warm and fuzzy when someone is shouting at you. And it is hard to feel warm and fuzzy when you have to shout at them. Emotions aside, the cost of unaided hearing loss has been estimated to be $2,500 annually in income for those with mild-moderate hearing loss and $5,600 annually for those with moderate loss (Sergei Kochkin, “The impact of untreated hearing loss on household income”). Nationally, this is perhaps $50 billion dollars in lost income.
Of the three reasons listed above for not buying hearing aids, the first can be handled by improving the sound quality of hearing aids and—most important—making every effort to induce expectations that are consistent with what the person will experience. In many cases, the person who does come in for hearing aids has two problems: inability to hear quiet sounds, and inability to hear in loud restaurants and the like. The first can be solved completely for most persons with most hearing aids. The second, when severe, can be solved by use of a remote FM or other microphone near the talker, where the signal-to-noise ratio at the microphone can be 20 dB better than at the listener's hearing aid microphone. A detailed discussion of “SNR loss” is beyond the scope of this application, but some 20% of all hearing aid wearers have sufficient SNR loss so they cannot understand speech in a noisy restaurant or cocktail party with or without their hearing aids. (Some report they hear better in those environments when they take their hearing aids off: It is so loud that everything is already audible, and their hearing aids make things even harder to understand.) If the pretty pictures and advertising copy lead people to expect they will hear better in noise with their hearing aids, those with severe SNR loss will surely be disappointed. Various lecturers have suggested that a satisfied person tells three other people, but a dissatisfied person tells 13 (one recent book title suggested a larger ratio: Peter Blackshaw, “Satisfied Customers Tell Three Friends, Angry Customers Tell 3,000).” To the extent that these ratios apply to hearing aid purchasing, even 20% of hearing aid purchasers may be sufficient to discourage a large portion of the 80% who don't purchase hearing aids. Industry statistics indicate some 15% of hearing aids are returned for credit as unsatisfactory to the purchaser. Some estimates indicate that another 14% end up in dresser drawers (Sergei Kochkin, “The VA and Direct Mail Sales Spark Growth in Hearing aid Market,” Hearing Review, December 2001).
Fortunately, it is not hard to prominently state in the description of a hearing aid that those with severe loss of ability to hear in noise will be able to hear quiet sounds better, but will need additional assistance in noisy surroundings. To the applicant's knowledge, no hearing aid advertisements make such a candid statement, but it is certainly just as appropriate for a low-cost hearing aid as for a hearing aid costing $3,000.
The second and third reasons for not obtaining hearing aids (need to see a professional and high cost) can be taken care of simultaneously, since the majority of the cost of hearing aids is the cost of the professional dispensing process. Before discussing the cost of a traditional hearing aid, it should be stated that this discussion is not in any way meant to disparage that process. There is no question that the means to the best possible hearing aid fitting is to see someone who understands hearing and hearing aids, and has demonstrated this understanding in the process of obtaining advanced degrees and a dispensing license. And much of the “soft” part of the dispensing is the teaching—which can only be done first hand—of the fact that the brain will “rewire” to accommodate the initially unnatural sound of the hearing aid and the fact that any change to the auditory input may make it sound to some new wearers as if they are listening to speech in a sea of noise. Not to mention simply putting the battery in right, which can be a major challenge for some persons. In good hands, the process is skilled, caring, and even so may require one or more readjustments of the hearing aid response or processing.
In traditional hearing aid fitting, there are two components to the “fitting” process: Taking impressions and obtaining an earmold (usually but not always custom) fitted to the external ear, plus adjusting the analog or digital signal processing to compensate for the individual characteristics of the hearing loss, for example, “flat loss” (approximately the same loss at all frequencies), “high frequency loss” (significantly greater loss at high frequencies than at low frequencies), “ski slope loss” normal or near normal low-frequency hearing with precipitous drop to moderate-severe high-frequency loss, etc. In the normal fitting of a hearing aid, the frequency response of the hearing aid is adjusted at each level to compensate for the loss at that level. Various “fitting formulae” have been developed to provide appropriate targets based on the shape and degree of the hearing loss. One such popular fitting target called FIG. 6 was developed by applicant Killion.
These two fitting processes typically require two or three visits and the attention of licensed skilled professionals, often with doctorate degrees. The advantage of the traditional fitting method is a better fitting than may be obtained in a one-size-fits-many ready-fit hearing aid design. The disadvantage is cost: The total cost of the basic hearing aid itself plus the professional fees typically add up to $3,000 to $8,000 for a pair of hearing aids.
For those who won't see a professional for a traditional hearing aid, however, the above advantages are never experienced: the person is without amplification. For such individuals, an inexpensive hearing aid that is simple to use, especially if a trial purchase is encouraged by allowing the purchaser to return the aid if they are not satisfied, may encourage a trial of hearing aids. Moreover, it seems likely that after experiencing the improved audibility of too-quiet sounds, those with sufficient resources may well be inclined to see a professional for even better hearing aids.
Interestingly enough, applicant Killion has had two recent conversations that suggest cost can be the deciding factor even when adequate funds are available. At the Oshkosh, Wis., EAA air show, a conversation around a picnic table with four pilots in their 60s and 70s indicated that all four could use hearing aids but had never gone to get them. When the discussion of a high-quality ready-fit hearing aid for $300 came up, all were interested and two said eagerly “tell me where I can get one.” All would try a do-it-yourself $300 hearing aid, yet none planned to go get a $3,000 hearing aid. Each of these men owned, or had previously owned, private airplanes costing in excess of $100,000. Similarly, at Chautauqua, N.Y., Institution, where the cost of registration, transportation and lodging for a week typically exceeded $2,500, a conversation around another picnic table with four high-intellect women in their 60s and 70s (one perhaps in her 80s) indicated that, again, all could benefit from hearing aids, but did not intend to go get one. Yet all were keenly interested in a $300 hearing aid of good quality (even if it didn't have all the digital features so popular today).
After concluding that cost and “seeing a professional” were major factors in discouraging many persons from seeking hearing aid help, applicant Killion, who has taught the advanced hearing aid electroacoustics course to Northwestern University audiological graduate students for 25 years, and his colleague, Dr. Gail Gudmundsen, who has dispensed over 10,000 hearing aids over the years, applied to the FDA for creation of a new category of hearing aid that can be purchased over the counter (“OTC”). See, http://webreprints.djreprints.com/1257230721151.html, Wall Street Journal. These OTC hearing aids were meant to be self-fitted by the self-selection of eartips, much as applicant Killion's company's high-fidelity earphones are fitted by the user as described, for example, in U.S. Pat. No. 5,887,070, entitled “High fidelity insert earphones and methods of making same,” issued to Iseberg et al., and on the Internet at http://www.etymotic.com/ephp/epcomp.aspx. The application to the FDA was denied, but the problem remains unsolved.
Applicant Killion has published three papers summarizing many probable reasons for hearing aid failure, but certainly the unnatural sound of many aids appears to be an important one. See Killion M C, “Myths that Discourage Improvements in Hearing Aid Design,” The Hearing Review, 11, No. 1, 32-40, 70, 2004; Killion M C, “Myths About Hearing in Noise and Directional Microphones,” The Hearing Review, 11, No. 2, 14-19, 72-73, 2004, and Killion M C, “Myths about Hearing Aid Benefit and Satisfaction,” The Hearing Review, 11, No. 8, 14-20, 66, 2004.
All of these considerations suggest that a low-cost one-size-fits-many hearing aid might result in substantially improved lives for many of those who don't presently obtain hearing aids but need them, especially if it minimized the need for several weeks of brain rewiring required to get used to the unnatural sound of some digital hearing aids.
A principle limitation has been the unavailability of a low-power output circuit compatible with the analog bipolar circuit used in K-AMP® hearing aids, which have required more costly Class D circuits. Also, while digital hearing aid circuits have employed switching outputs comparable in efficiency to Class D switching outputs, the overhead current for digital circuits is large, wiping out the possible advantage to the switching output. Finally, battery life of many digital hearing aids is only one week and that of many Completely In the Canal (“CIC”) hearing aids is often only 3 days.
Thus, there is a need for a low-cost hearing aid that exhibits acceptable performance characteristics including improved sound quality and extended battery life.